1. CHE 1316 Laboratory Measurements & Techniques
LECTURE 1
Course Introduction
Intro to Quantitative Analysis
Units of Measurement
Solutions and Concentrations
Stoichiometric Calculations
(Review Chaps. 3 & 4)
LECTURE 2
Intro to Titrimetric Analysis
Analytical Standards
Calculations of Titrimetric Analysis
(Acids & Bases)

2. Stoichiometric Calculations
Hill, Petrucci, et al., General Chemistry…CHAPTER 3
Stoichiometric Ratio
correction: “B”
x A + y B → products OR
x A + z C → y B
mol B = mol A ×
y mol B
x mol A
mol = mass/molar mass
mol = concentration × volume

3. Titrimetric Methods
Hill, Petrucci, et al., General Chemistry…SECTION 4.6
Titration: Solution (titrant) is added from buret into a titration vessel containing substance being titrated (analyte). Purpose is to determine the volume of titrant required to exactly react with the analyte.
Equivalence Point: The point in a titration at which exactly enough titrant has been added to react with all of the analyte.
End Point: That point in a titration at which some detectable change occurs signaling that the equivalence point has been reached.
Titration Error: Difference between volume of titrant at the end point and the volume at the equivalence point.
Et = Vep − Veq

4. Analytical Standards
Titrimetric analyses depend upon a knowledge of the exact amount of either the titrant added or of the substance being titrated
Primary Standard: A solid of such purity that a standard solution can be prepared by dissolving the solid in a solvent and diluting to a known volume of solution.
High purity. Typically  99.9%
Stable in air. No rxns. with H2O, CO2, O2
No waters of hydration. (NiCl2 6H2O)
Readily available at modest cost.
Reasonable solubility. Typically  0.01 M
Large Molar Mass
Secondary Standard: Solution must be standardized by titration with/of a primary standard.
e.g., Sodium Hydroxide (NaOH):
Low Purity
Absorbs Water Rapidly. Hygroscopic
Reacts with CO2
Low Molar Mass (40 g/mol)
Weight (g) / Molar Mass (g/mol)
Direct Method: M (mol/L) =
Volume (L)

5. Standard Solution Properties
Stable (i.e., concentration constant over time)
Reacts rapidly with analyte
Reacts completely with analyte
Reacts selectively with analyte
Reacts with known stoichiometry (i.e., must know balanced chemical eqution)

6. Volumetric Calculations
x A + y B → products
mol B = mol A ×
y mol B
x mol A
Fundamental Relationship of Titrimetric Analysis: applies only at the equivalence point of the titration (titrate soln. of A with soln. of B):
mol titrant = mol analyte × stoichiometric ratio
(MEMORIZE!!!)
Example: Standardization of HCl with Na2CO3:
Na2CO3(s) HCl(aq) → 2 NaCl(aq) + CO2(g) + H2O(l)
Dissolve g of primary standard grade Na2CO3(s) in mL of water.
Pipet mL of this solution into a flask and titrate with an HCl(aq) solution.
40.00 mL of titrant are required to achieve the end point.
Determine the concentration of HCl.

7. Volumetric Calculations
Primary Standard Solution of Na2CO3: M
At the Equivalence Point of Titration:
5.000 g / g mol−1 L
CNa2CO3 =
mass / molar mass
volume =
mol titrant = mol analyte × stoichiometric ratio
2 mol HCl
mol HCl = mol Na2CO3 ×
1 mol Na2CO3
2 mol HCl
CHCl × VHCl = CNa2CO3 × VNa2CO3 ×
1 mol Na2CO3
2 mol HCl
CHCl × L = M × L ×
1 mol Na2CO3
CHCl = M

8. Problem 7, p. 115
Consider the titration of ferrous ammonium sulfate with potassium permanganate which proceeds according to the following reaction:
10 Fe(NH4)2(SO4) KMnO H2SO4 →
2 MnSO Fe2(SO4) (NH 4)2SO4 + K2SO H2O
Write an equation describing the quantitative relationship between the concentration of ferrous ammonium sulfate and the concentration of potassium permanganate, including the stoichiometric ratio which applies at the equivalence point of this redox titration.
Step 1: Identify the titrant and analyte and arrange them in the form of the equality that is true at the equivalence point of the titration.
2 mol KMnO4
mol KMnO4 = mol Fe(NH4)2(SO4)2 ×
10 mol Fe(NH4)2(SO4)2

9. Problem 7, p. 115
Step 2: Expand the previous equation using the equality
Concentration (C) × volume (V) = mol:
C(KMnO4) × V(KMnO4) = C(Fe(NH4)2(SO4)2) × V (Fe(NH4)2(SO4)2) × 2/10
Don’t forget the
stoichiometric ratio!!!
You will typically be dealing with concentration and volume when considering the titrant in your analyses (and in ‘practical’ problems that your are asked to work).

10. Problem 10, p. 116 Step 1: Step 2: (for NaOH)
Write an equation describing the quantitative relationship between the weight of H4C10H12O8N2 and the concentration of NaOH, including the stoichiometric ratio, which applies at the equivalence point of the following acid-base titration:
4 NaOH + H4C10H12O8N2 → Na4C10H12O8N H2O
Step 1:
mol NaOH = mol H4C10H12O8N2 ×
4 mol NaOH
1 mol H4C10H12O8N2
Step 2: (for NaOH)
C(NaOH) × V(NaOH) = mol H4C10H12O8N2 × 4/1
How do we include the weight of H4C10H12O8N2?

11. Problem 10, p. 116
Step 3: Expand “mol H4C10H12O8N2” in the previous equation using the equality:
mass divided by molar mass equals moles…
(i.e., grams/grams mol−1 = mol)
C(NaOH) × V(NaOH) = × 4/1
g H4C10H12O8N2
MW H4C10H12O8N2
PRACTICE SUGGESTED PROBLEMS FOR NEXT TIME

12. Suggested Problems
Problem Set 1: p. 114 of your RED laboratory manual:
1, 3, 4c-g, 5-7, 10-12, 15-17, 19, 21, 23, 25, 26, 28, 30, 32
Note that listing is slightly modified from your syllabus…
Answers are given on pp …